1. Field of the Invention
The present invention relates to a printing apparatus, a control method therefor, and a storage medium storing a control program therefor, and in particular, relates to a printing method of printing with inks of a plurality of colors, such as yellow (Y), magenta (M), and cyan (C), and of printing with the inks of the plurality of colors again.
2. Description of the Related Art
A thermal sublimation printing apparatus attracts attention in recent years as a printing apparatus that prints a photograph (an image) obtained by an image pickup apparatus, such as a digital camera. A thermal sublimation printing apparatus makes thermal sublimation ink ribbons in yellow (Y), magenta (M), and cyan (C) be in pressure contact with a printing sheet with a thermal head and a platen roller. Then, the printing sheet is transferred while exothermic elements of a thermal head are selectively heated in a press contact state, which sublimates ink on the ink ribbons to make the ink adsorb to the printing sheet and expresses a tone.
In this printing apparatus, when printing with one color is completed, the printing sheet is again returned to a print starting position, and prepares for printing of the next color. Then, an overcoat layer is formed on the printing sheet with transparent thermally fused material as a protective layer after finishing the printings in yellow (Y), magenta (M), and cyan (C). As a result, the printed matter is protected.
In printing, a thermal sublimation ink ribbon on which yellow (Y), magenta (M), cyan (C), and overcoat (OC) sections are arranged continuously is used. In order to detect a head of each color section, two head markers are formed at the starting point of the yellow section, and one head marker is formed at the starting point of each of the magenta (M), cyan (C), and overcoat (OC) sections, for example.
The head markers of the yellow (Y) section are detected first. Then, the head marker of the magenta (M) section, the head marker of the cyan (C) section, and the head marker of the overcoat (OC) section are sequentially detected. Accordingly, printing is certainly started from the yellow, which is the first color.
Above-mentioned printing method employs three ink sheets in total, i.e., one yellow (Y) ink sheet, one magenta (M) ink sheet, and one cyan (C) ink sheet. On the other hand, there is a printing method that repeats printing twice using two sets of yellow (Y), magenta (M), and cyan (C) ink sheets (six sheets) in order to raise the highest attained density of printed matter, for example (see Japanese Laid-Open Patent Publication (Kokai) No. 2007-276259 (JP 2007-276259A)).
However, since the printing apparatus disclosed in the above-mentioned publication repeats the same printing process twice, it is difficult to obtain density more than density that is obtained by repeating the printing process twice. That is, the conventional printing apparatus needs to further repeat the printing process if further deep print density is desired.